As shown in JP-10-220272A (U.S. Pat. No. 6,142,121), in a common rail type fuel injection system constructed of this fuel injection apparatus, fuel pressure-fed from a fuel pump is accumulated in a high-pressure state by a common rail. Then, the accumulated high-pressure fuel is supplied to the fuel injection valve of each cylinder through pipes (high-pressure fuel passage) disposed for each cylinder. The common rail is provided with a fuel pressure sensor (rail pressure sensor). This system is constructed in such a way as to control various devices constructing a fuel supply system on the basis of the output of the rail pressure sensor.
The output value of the rail pressure sensor is converted into the pressure. However, this converted pressure does not always agree with an actual pressure value. That is, the pressure converted from the output value may deviate from an actual pressure value due to an individual difference of the fuel pressure sensor, which is caused by a manufacturing error or a designing error. Even if the fuel pressure deviates from the actual pressure values such a deviation is not compensated in a conventional fuel injection system. Robustness with respect to the output value is not enough. The fuel injection system is not accurately controlled.